发个网址缩短的PHP代码

function numToStr($num)
{
$out = "";

for ( $t = floor(log10($num) / log10(62)); $t >= 0; $t-- )
{
$a = floor($num / pow(62, $t));

$out = $out . substr("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",$a,1);

$num = $num - ($a * pow(62,$t));
}

return $out;
}

function strToNum($str)
{
$out = 0;

$len = strlen($str) - 1;

for ( $t = 0; $t <= $len; $t++ )
{
$out = $out + strpos("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",substr($str,$t,1))*pow(62,$len-$t);
}

return $out;
}